Polishing Slurry

ABSTRACT

The present invention provides a polishing slurry which remarkably inhibits the occurrence of scratch, dishing or erosion. According to the present invention, provided is a polishing slurry comprising organic particles (A), an oxidizing agent and a complexing agent, wherein said organic particles (A) are those obtained by coating a part of the surface of an organic particle (B) having functional groups capable of reacting with a metal to be polished on the surface with a resin (C) free from functional groups capable of reacting with a metal to be polished, and the organic particle (B) is preferably one containing a copolymer obtained by polymerization of a monomer composition comprising 1 to 50 weight % of one, two or more monomers selected from a monomer having a carboxyl group, a monomer having a hydroxyl group, a monomer having an amino group, a monomer having an acetoacetoxy group and a monomer having a glycidyl group, and 99 to 50 weight % of other monomers, with each percentage based on the total weight of the monomers.

TECHNICAL FIELD

The present invention relates to a polishing slurry which is capable ofpolishing without damaging a surface of copper or the like for smoothingthe surface in the formation of wiring comprising copper or the likeused in the manufacture of semiconductor devices.

BACKGROUND ART

In late years, in a wiring process in the manufacture of semiconductordevices, as a technique for forming grooves for forming wiring on aninsulation film and backfilling a metal film for wiring by the platingmethod, removing an excess metal film and smoothing an insulation filmincluding metal wiring, CMP (Chemical and Mechanical Polishing) has beenused. This is a method comprising mechanically polishing by a slurrywith abrasive particles dispersed therein.

In the CMP technique, a slurry containing inorganic abrasive particlesmade of metal oxides such as ceria, alumina and the like or silica hasconventionally been used. However, these inorganic abrasive particleshave high hardness. When a metal film with low hardness such as copperor the like is polished, the inorganic abrasive particles-have thereforepresented a big problem of creating abrasive damages on a metal surfacecalled scratches or causing a phenomenon called erosion of formation inconcave shapes by further polishing the metal film in the center of adense area of wiring pattern including an insulation film of an undercoat layer.

At present, in order to improve performance of semiconductors, the ½width of wiring on the insulation film becomes much finer from 130 nm to90 nm and even to 65 nm, and the surface of the insulation film to bepolished is in a much complicated structure. If the width of wiringbecomes much finer, abrasive damages on the metal surface due toscratches cause an open circuit, and dishing or erosion causes anincrease in wiring resistance or deviation and a short circuit betweenwirings, thereby considerably deteriorating the reliability ofsemiconductor devices and drastically lowering the product yields.

This scratch is created by partial excess polishing generated by thehardness of abrasive particles or the existence of aggregated masses ofabrasive particles.

Furthermore, erosion is created because of excess polishing by usinghard abrasive particles, or a low polishing selectivity to an under coatlayer such as an insulation film or a barrier layer for preventingdiffusion of a metal.

In order to solve these problems, in case of inorganic abrasiveparticles, silica particles which are softer than alumina particles areused as abrasive particles, and a polishing solution which is made fromneutral to alkaline without elution of a metal for polishing has beendeveloped. For example, when silica is used as abrasive particles,scratches are reduced as compared to alumina, but when inorganicabrasive particles are used, occurrence of scratches or erosion cannotbe prevented. So, the problems cannot be fundamentally solved.

Meanwhile, in late years, since the solid content in a polishing agentremains on the insulation film, the increasing total dielectric constantof the insulation film layer has been mentioned as a problem. Anexisting polishing agent composed of the alumina or silica as abrasiveparticles has the heat resistant property equivalent to that of theinsulation film so that the solid content cannot be removed by thermaltreatment but it can only be removed by using a washing solution. Sincethis removal by using a washing solution is a method for removingresidual abrasive particles by slightly dissolving the insulation film,damage to the insulation film is great, which becomes a problem.

On the other hand, in U.S. Pat. No. 3,172,008, there has been discloseda method employing particles of an organic polymer compound as abrasiveparticles. In the organic polymer used therein, since components freefrom functional groups such as a methacryl resin, a polystyrene resinand the like are used for abrasive particles, and the organic polymerdoes not contain an oxidizing agent for oxidizing the metal surface, achemical action with a metal film to be polished never takes place.Thus, a polishing rate required for or sufficient for a wiring processin the manufacture of semiconductor devices is not obtained.

In order to solve the above problems regarding particles of the organicpolymer compound, for example, in Japanese Patent Laid-open No.2001-55559, there has been disclosed an aqueous dispersion for CMPcontaining organic particles having functional groups capable ofreacting with a metal forming a surface to be polished. However, aphenomenon called dishing of formation in concave shapes by furtherpolishing a metal film on wiring portion in the center is not solved. Inorder to prevent this, a technique using a protective-film forming agentsuch as benzotriazole or the like is disclosed in Japanese PatentLaid-open No. 1996-83780 and the like. However, since theprotective-film forming agent such as benzotriazole or the like ishighly effective, there is a drawback such that the polishing rate isremarkably lowered.

Patent Document 1: U.S. Pat. No. 3,172,008

Patent Document 2: Japanese Patent Laid-open No. 2001-55559

Patent Document 3: Japanese Patent Laid-open No. 1996-83780

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a polishing slurrycontaining specific organic particles which is remarkably inhibited inthe occurrence of scratch, dishing or erosion.

In order to solve the above object, the present inventors have conductedan extensive study and as a result, have completed the presentinvention. That is, the present invention relates to a slurry comprisingorganic particles (A), wherein said organic particles (A) are thoseobtained by coating a part of the surface of an organic particle (B)having functional groups capable of reacting with a metal to be polishedon the surface with a resin (C) free from functional groups capable ofreacting with a metal to be polished.

The above polishing slurry comprising an oxidizing agent is a preferredembodiment because it promotes the reaction of the metal to be polishedwith the functional groups.

The organic particle (B) containing a copolymer obtained bypolymerization of a monomer composition comprising 1 to 50 weight % ofone, two or more monomers selected from a vinyl monomer having acarboxyl group, a vinyl monomer having a hydroxyl group, a vinyl monomerhaving an amino group, a vinyl monomer having an acetoacetoxy group anda vinyl monomer having a glycidyl group, and 99 to 50 weight % of othervinyl type monomers, with each percentage based on the total weight ofthe monomers is a preferred embodiment because it promotes the reactionwith a metal to be polished.

Furthermore, the resin (C) containing a polymer of a styrene typemonomer and/or a (meth)acrylic acid ester type monomer is a preferredembodiment because it controls the reaction with a metal to be polished.

Further, the above polishing slurry further comprising at least onecomplexing agent selected from carboxylic acids, amines, amino acids andammonia, and having its pH in the range of 5 to 11 is a preferredembodiment from the viewpoint of the polishing rate.

Meanwhile, the oxidizing agent being hydrogen peroxide is a preferredembodiment from the viewpoint of the smoothness.

EFFECT OF THE INVENTION

The polishing slurry of the present invention is capable of polishing anexcess metal film on a wiring pattern-formed insulation film with a highrate, capable of polishing without causing any damage or scratch due topolishing excess on the surface of a substance to be polished, andcapable of polishing which produces high smoothness of the surfacewithout any unevenness due to dishing, erosion or the like.

Further, since the polishing slurry of the present invention containingorganic fine particles has a considerably lower decompositiontemperature than that of the insulation film, it is possible to removethe residue of the polishing slurry without damaging the insulation filmby thermal treatment or plasma treatment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view illustrating a SEM image of organic particles obtainedin Production Example 1.

FIG. 2 is a view illustrating a SEM image of organic particles obtainedin Comparative Production Example 1.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will be described in more detail below.

(Organic Particles)

The organic particles (A) are those obtained by coating a part of thesurface of an organic particle (B) having functional groups capable ofreacting with a metal to be polished with a resin (C) free fromfunctional groups capable of reacting with a metal to be polished.

In the present invention, “capable of reacting with a metal to bepolished” means a capability of promoting a polishing rate of a metal tobe polished by a chemically reactive action.

Examples of the functional group capable of reacting with a metal to bepolished of the organic particle (B) include a carboxyl group, ahydroxyl group, am amine group, a ketone group, a glycidyl group and anacetoacetoxy group. Particularly preferably used is a carboxylic acid.

The organic particle (B) can be produced, for example, by polymerizationof a monomer having functional groups capable of reacting with thesemetals to be polished and other vinyl type monomers capable ofcopolymerization with the monomer. In case of organic particles having aparticularly preferable carboxyl group, it is preferable that analkaline substance of not less than 0.3 mole equivalent is added on thebasis of the carboxyl group in the obtained copolymer emulsion fordissociating the carboxyl group, to easily form a complex with a metal.

Examples of the carboxyl group-containing vinyl monomer used in thepresent invention include one, two or more kinds selected fromunsaturated monobasic acids such as an acrylic acid, a methacrylic acid,a crotonic acid and the like; unsaturated dibasic acids such as anitaconic acid, a fumaric acid, a maleic acid and the like; or monoestersthereof. Particularly preferably used are an acrylic acid and amethacrylic acid.

Examples of the hydroxyl group-containing vinyl monomer include2-hydroxyethyl(meth)acrylate, 2-hdyroxypropyl(meth)acrylate,2-hydroxybutyl(meth)acrylate, 4-hydroxybutyl(meth)acrylate and the like.

Examples of the amino group-containing vinyl monomer include aminogroup-containing (meth)acrylate type monomers containing a tertiaryamino group. Examples thereof includeN,N-dimethylaminoethyl(meth)acrylate,N,N-dimethylaminopropyl-(meth)acrylate,N,N-t-butylaminoethyl(meth)acrylate,N,N-monomethylaminoethyl(meth)acrylate and the like.

Further, N-alkyl amino (meth)acrylamide containing a tertiary aminogroup is employed. Examples thereof includeN,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide,N,N-dimethylaminopropyl(meth)acrylamide,N,N-dimethylaminoethyl(meth)acrylamide, N-isopropyl(meth)acrylamide andthe like.

Examples of the acetoacetoxy group-containing vinyl monomer includeacetoacetoxyethyl (meth)acrylate and the like. Examples of the glycidylgroup-containing vinyl monomer include glycidyl(meth)acrylate and thelike.

The amount of the monomer having functional groups capable of reactingwith these metals to be polished is preferably from 1 to 50 weightparts, more preferably from 3 to 45 weight parts, and most preferablyfrom 5 to 40 weight parts based on the total monomer components in thecopolymer. When the amount is less than 1 weight part, the intendedpolishing rate might not be achieved. Further, when the amount exceeds50 weight parts, water resistance and alkali resistance might be bad insome cases.

Examples of other vinyl type monomers capable of copolymerization with amonomer having functional groups capable of reacting with theaforementioned metal to be polished include styrene type monomers suchas styrene, α-methylstyrene, vinyl toluene and the like; (meth)acrylicacid ester type monomers such as methyl(meth)acrylate,ethyl(meth)acrylate, butyl(meth)acrylate, 2-ethylhexyl(meth)acrylate,isopropyl(meth)acrylate, isobutyl(meth)acrylate, t-butyl(meth)acrylate,n-hexyl(meth)acrylate, octyl(meth)acrylate, cyclohexyl(meth)acrylate,isobornyl(meth)acrylate and the like; vinyl esters such as vinylacetate, vinyl propionate and the like; vinyl cyanides such as(meth)acrylonitrile and the like; and halogenated vinyl compounds suchas vinyl chloride, vinylidene chloride and the like. Further, inaddition to the carboxyl group-containing vinyl monomer as a functionalgroup monomer, (meth)acrylamide or N-methylol(meth)acrylamide and thelike are used as needed.

The amount of other vinyl type monomers to be used is preferably from 99to 50 weight % and more preferably from 95 to 70 weight %.

Such organic particles may be those swelling by adding an alkalinesubstance or those without swelling. But, either of organic particlesmay be used. Further, “swelling” mentioned herein means the increasingaverage particle diameter of the primary particle by containing water orother water-soluble substances in the molecule without causingdecomposition or cohesion.

In order to adjust the degree of swelling of organic particles by theaddition of alkali, as needed, a crosslinking monomer can becopolymerized. The crosslinking monomer is a monomer containing 2 ormore polymerizable unsaturated bonds in a molecule. Examples thereofinclude divinyl benzene, butadiene, ethylene glycol dimethacrylate,trimethylol propane trimethacrylate, ethylene glycol diacrylate,1,3-butylene glycol dimethacrylate, diacrylate and the like. The amountof the crosslinking monomer to be used is preferably not more than 20weight % and more preferably not more than 10 weight % in the totalmonomers. The crosslinking monomer is properly used depending on thekind of the unsaturated monomer having functional groups capable ofreacting with a metal to be polished, its amount, the kind of the vinyltype copolymer and the like.

The resin (C) to be coated on the surface of the organic particle (B) iscomposed of a polymer free from functional groups capable of reactingwith a metal to be polished, and preferably composed of a polymer of astyrene type monomer and/or a (meth) acrylic acid ester type monomer.Specific examples of the styrene type monomer and (meth)acrylic acidester monomer include a monomer having functional groups capable ofreacting with the aforementioned metal to be polished and other vinyltype monomers capable of copolymerization.

A method for the synthesis of the organic particles is not particularlylimited, but the organic particles can be, for example, synthesized bymulti-stage polymerization of emulsion polymerization. That is, therecan be used a method comprising synthesizing the organic particle (B)having functional groups capable of reacting with a metal to be polishedand then additionally synthesizing the polymer (C) free from functionalgroups capable of reacting with a metal to be polished, or, to thecontrary, a method comprising synthesizing the polymer (C) free fromfunctional groups capable of reacting with a metal to be polished andthen additionally synthesizing the organic particle (B) havingfunctional groups capable of reacting with a metal to be polished.

The amount of the monomer is adjusted such that a part of the surface ofthe organic particle (B) is coated with the resin (C). A part of thesurface of the organic particles may be coated with the resin (C).Preferably 10% or more but less than 100% of the surface is coated, andmore preferably 30% or more but less than 95% of the surface is coated.The coating ratio of the surface can be measured by SEM.

By coating the surface of the organic particle (B) with the resin (C),scratches or erosion can be inhibited.

The particle diameter at a state that the organic particles (B) arecoated with the resin layer (C) is preferably from 10 to 5,000 nm andmore preferably from 30 to 300 nm. Further, the molecular weight of theorganic particles (B) is preferably from 10,000 to 5,000,000 and morepreferably from 100,000 to 1,000,000. The molecular weight of the resin(C) is preferably from 1,000 to 1,000,000 and more preferably from10,000 to 500,000.

The content of the organic particles in the polishing slurry is varieddepending on the kind of the organic fine particle, but it is preferablyfrom 0.1 to 20 weight %. When the content is less than 0.1 weight %, theeffect of the organic fine particles cannot be fully exhibited so thatthe intended polishing rate cannot be achieved in some cases. Further,when the content is more than 20 weight %, the viscosity of thepolishing slurry is high so that it becomes difficult to supply thepolishing slurry at a predetermined rate upon polishing in some cases.

Since metal components, particularly impurity components such as sodium,potassium, iron, magnesium and the like contained in the polishingslurry have an influence on the stability of the polishing rate, it isrequired to inhibit such components to not more than 1 ppm by adding anoxidizing agent such as hydrogen peroxide or the like.

In order to obtain an aqueous dispersion of organic particles free froma metal, a monomer, a dispersing agent such as a surfactant and thelike, a polymerization initiator and other additives, which are freefrom a metal can be used for its production.

Examples of the dispersing agent free from a metal include water-solublepolymers such as polyvinyl alcohol, modified polyvinyl alcohol,polyvinyl pyrrolidone, (meth)acrylic acid (co)polymer,poly(meth)acrylamide (co)polymer, ethylene glycol and the like. Examplesof the surfactant include an anionic surfactant, a non-ionic surfactantand a cationic surfactant. The anionic surfactant has an acidic groupsuch as a sulfonic acid, a carboxylic acid or the like as a hydrophilicgroup, but those without containing metal salts such as Na, K or thelike as its counter ion can be used. Generally used are ammonium salts.Examples thereof include ammonium salts such as dodecylbenzenesulfonicacid, lauryl sulfuric acid, alkyl diphenyl ether disulfonic acid, alkylnaphthalene sulfonic acid, dialkyl sulfosuccinic acid, stearic acid,oleic acid, dioctyl sulfosuccinate, polyoxyethylene alkyl ether sulfuricacid, polyoxyethylene alkyl ether sulfuric acid, polyoxyethylene alkylphenyl ether sulfuric acid, dialkyl sulfosuccinic acid, stearic acid,oleic acid, tert-octylphenoxyethoxypolyethoxyethyl sulfuric acid and thelike.

Furthermore, the greater part of the nonionic surfactants generally hasan ethylene glycol chain as a hydrophilic group, and does not contain ametal. Examples thereof include polyoxyethylene lauryl ether,polyoxyethylene octylphenyl ether, polyoxyethylene oleylphenyl ether,polyoxyethylene nonylphenyl ether, oxyethylene-oxypropylene blockcopolymer, tert-octylphenoxyethylpolyethoxyethanol,nonylphenoxyethylpolyethoxyethanol and the like.

Meanwhile, examples of the cationic surfactant include lauryl trimethylammonium chloride, stearyl trimethyl ammonium chloride, cetyl trimethylammonium chloride, distearyl dimethyl ammonium chloride, alkyl benzyldimethyl ammonium chloride, lauryl betaine, stearyl betaine, lauryldimethyl amine oxide, lauryl carboxy methyl hydroxy ethyl imidazoliniumbetaine, coconut amine acetate, stearyl amine acetate, alkyl amineguanidine polyoxy ethanol, alkyl picolinium chloride and the like. Thesedispersing agents can be selected singly or in combination of 2 or morekinds.

Examples of the polymerization initiator free from a metal include azocompounds such as hydrogen peroxide, ammonium persulfate,azobiscyanovaleric acid,

-   2,2′-azobis(2-amidinopropane)dihydrochloride,-   2,2′-azobis[2-(N-phenylamidino)propane]dihydrochloride,-   2,2′-azobis{2-[N-(4-chlorophenyl)amidino]propane}dihydrochloride,-   2,2′-azobis{2-[N-(4-hydroxyphenyl)amidino]propane}dihydrochloride,    2,2′-azobis[2-(N-benzylamidino)propane]dihydrochloride,    2,2′-azobis[2-(N-allylamidino)propane]dihydrochloride,-   2,2′-azobis{2-[N-(2-hydroxyethyl)amidino]propane}dihydrochloride,    azobisisobutyronitrile,-   2,2′-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propionamide},-   2,2′-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)ethyl]propionamide},    2,2′-azobis[2-methyl-N-[2-hydroxyethyl]propionamide],-   2,2′-azobis(isobutyramide)dihydrate and the like; and organic    peroxides such as cumene hydroperoxide, t-butyl hydroperoxide,    benzoyl peroxide, t-butylperoxy-2-ethylhexanoate, t-butylperoxy    benzoate, lauroyl peroxide and the like. One, two or more kinds    thereof can be selected. As the initiator, preferably used are    water-soluble initiators, and more preferably used are ammonium    persulfate, azobiscyanovaleric acid and-   2,2′-azobis(2-amidinopropane)dihydrochloride. The amount of the    initiator to be used in general is from 0.1 to 5 weight %, based on    the total weight of the monomer to be (co)polymerized.

Furthermore, when obtaining organic particles, mercaptans such ast-dodecyl mercaptan, n-dodecyl mercaptan and the like; and allylcompounds such as allyl sulfonic acid, methallyl sulfonic acid, sodiumsalts thereof and the like can also be used as a molecular weightregulating agent, as needed.

Organic particles can be prepared by an emulsion polymerization method,a suspension polymerization method and a mechanical emulsificationmethod which are known from the past. Examples of the emulsionpolymerization method include a method for polymerization of variousmonomers to be fed at a time and a method for polymerization whilecontinuously supplying monomers, in the presence of a dispersing agentand an initiator. The polymerization is usually carried out at atemperature of from 30 to 90 degree centigrade and an aqueous dispersionof organic particles is substantially obtained. The emulsionpolymerization method is a more preferable polymerization method sinceorganic particles with small particle diameters and excellent in thedispersion stability are obtained.

An acryl resin emulsion is most preferably used because it is excellentin the dispersability, and it does not generate separation (generationof supernatant and precipitation), or aggregated masses due to the lapseof time found in a polishing agent with organic fine particles such asmethacryl resin, phenol resin, urea resin and the like, in addition toalumina, silica or emulsion as abrasive particles, and resulting inobtaining stable polishing rates at all times.

(Complexing Agent)

As a complexing agent, a water-soluble compound capable of forming acomplex with a metal is preferable. Examples thereof include carboxylicacids such as acetic acid, oxalic acid, malic acid, tartaric acid,succinic acid, citric acid and the like; amines such as methylamine,dimethylamine, triethylamine, ethylamine, diethylamine, triethylamineand the like; amino acids such as glycine, asparatic acid, glutamicacid, cysteine and the like; ketones such as acetylacetone and the like;and nitrogen-containing cyclic compounds such as imidazole and the like.Preferably used are oxalic acid, malic acid and ethylamine.

The content of the complexing agent is varied depending on the kind ofthe complexing agent, but it is preferably in the range of 0.1 to 10weight % in the polishing slurry. When the content is less than 0.1weight %, the intended polishing rate might not be achieved in somecases because its effect is not fully exhibited. Further, when thecontent exceeds 10 weight %, dishing causing elution of a metal to bepolished other than the target polishing might not be inhibited in somecases because formation of a complex with a metal to be polished isexcessively progressed.

A metal to be polished forms a metal complex with a functional groupand/or a complexing agent contained in organic fine particles, wherebygood metal polishing is carried out. The metal complex may be composedof a ligand of organic fine particles and a ligand of a complexingagent, formation of a complex of organic fine particles and a metal maypromote formation of a complex of a complexing agent and a metal, orformation of a complex of a complexing agent and a metal may promoteformation of a complex of organic fine particles and a metal.

(Oxidizing Agent)

As an oxidizing agent, preferably used are potassium iodate and hydrogenperoxide, and more preferably used is hydrogen peroxide. The content ofthe oxidizing agent is preferably in the range of 0.1 to 15 weight % andparticularly preferably in the range of 0.5 to 5 weight % in a polishingcomposition. When the content is less than 0.1 weight %, a chemicalreaction of a metal with organic particles does not progress so that itis not possible to achieve the intended polishing rate in some cases.Further, when the content exceeds 15 weight %, an oxide film formed on ametal surface might be passivated for preventing the progress ofpolishing so that it is not possible to achieve the intended polishingrate in some cases.

(pH)

The pH of the polishing slurry of the present invention is preferably inthe range of 5 to 11 and more preferably in the range of 7 to 10. Whenthe pH of the polishing slurry is less than 5, elution of a metal cannotbe inhibited so that dishing might occur in some cases. On the otherhand, when the pH is above 11, an insulation film is dissolved orpartially decomposed in some cases when a semiconductor insulation filmand metal wiring are on the same surface, which is the final point inpolishing a metal film.

Substances used for the pH adjustment of the polishing agent are notparticularly limited. Examples of alkaline substances include aminessuch as ammonia, triethylamine, diethylamine, ethylamine,trimethylamine, dimethylamine, methylamine and the like; and inorganicsubstances such as NaOH, KOH and the like. Further, examples of acidicsubstances include inorganic substances such as hydrochloric acid,nitric acid and the like; and organic acids such as acetic acid, oxalicacid, citric acid and the like. The pH regulating agent may also be usedas a complexing agent that can be a ligand of the aforementioned metals.Further, these substances may be used in combination of 2 or more kinds.

(Production Method of Polishing Slurry)

To produce the polishing slurry, for example, organic fine particles, acomplexing agent, an oxidizing agent and water are mixed and then the pHof the mixture is adjusted to produce a slurry which is used as apolishing agent. This production method is not particularly limited, butit is preferable that an pH-adjusted aqueous solution of a complexingagent capable of forming a ligand with a metal is added to a pH-adjustedresin emulsion and the resulting mixture is well stirred and mixed.Then, an oxidizing agent is added thereto little by little, and furtherstirred and mixed.

After finally adjusting the pH and concentration of the mixture,insoluble substances and aggregated masses are removed therefrom byfiltering using a filter paper to have a polishing agent.

(Additive)

Examples of the additive include nitrogen-containing heterocyclic ringcompounds such as benzotriazole, quinaldic acid and the like;water-soluble polymers such as polyacrylic acid, polyvinyl alcohol,polyethylene glycol, glucose and the like; and substances such as asurfactant and the like. These additives may be added singly or incombination of 2 or more kinds. The amount to be added and the kind ofthe additives are not particularly limited as far as the object of thepresent invention can be achieved.

EXAMPLES

The present invention is now more specifically illustrated below withreference to Examples. Incidentally, in these Examples, part (s) and %refer to weight part (s) and weight % unless otherwise particularlymentioned.

A particle diameter of an organic particle in a polishing compositionwas measured by the following method.

(Particle Size Distribution Measurement Method using Principle of LaserDynamic Light Scattering Method)

Measurement Device: MICROTRAC UPA Model: 9230 (a product of Leeds andNorthrup)

Concentration Condition: crude sample solution

Measurement Time: 900 seconds

A polishing slurry was evaluated according to the following methods.

1. Evaluation of Polishing Rate

Polishing slurry: polishing composition of the present invention

Substance to be polished: 8-inch silicon wafer in which 5,000 Å of athermal oxide film, 300 Å of a Ta film formed by the sputtering method,1,500 Å of a seed copper film for plating formed by the CVD method,15,000 Å of a copper film formed by the plating method are laminated ona substrate of the silicon wafer

Polishing device: Lapmaster LGD-15

Polishing pad: 340 mm IC-1000/suba400 grid

Polishing load: 2 psi

Polishing time: 1 min.

Slurry supplying rate: 15 cc/min

Table rotation speed: 60 rpm

Head rotation speed: 60 rpm

1) Calculation of Polishing Rate

A substance to be polished was subjected to ultra pure water washing andultrasonic cleaning, and then dried. A film thickness was measuredbefore and after polishing by measuring sheet resistance using a 4-pointprobe. An average polishing rate was calculated from the change in thefilm thickness and polishing time.

2) Surface Defects

The polished substance was washed with ultrapure water and dried, andthen its surface was observed using a differential interference contrastmicroscope with a magnification of x2500. Incidentally, damage on thesurface having a length of not less than 0.1 μm was determined as ascratch.

∘: 5 scratches or less

X: more than 5 scratches

2. Measurement of Amount of Dishing

A groove having a thickness of 5,000 Å and a width of 100 μm was formedon an oxide film on the silicon wafer by dry etching. Copper wasembedded into this groove by the plating method to have a substance tobe polished. Using the polishing composition of the present invention,the substance was polished under the above polishing conditions, andthen a thickness of a concave in the center of the groove was measuredby a cross-sectional SEM photograph. Incidentally, polishing wasfinished at the time when copper polishing of a part in which the groovewas not formed was completed.

3. Measurement of Amount of Erosion

A plurality of grooves having a thickness of 5,000 Å and a width of 4.5μm were formed at intervals of 0.5 μm on an oxide film on the siliconwafer by dry etching. Copper was embedded into these grooves by theplating method to have a substance to be polished. Using the polishingslurry of the present invention, the substance was polished under theabove polishing conditions, and then the height difference between agroove in the center and grooves on both sides was measured by across-sectional SEM photograph. Polishing was finished at the time whencopper polishing of a part in which the groove was not formed on bothsides of the groove was completed.

4. Evaluation of Storage Stability

A polishing agent was allowed to stand for 6 hours at atmosphericpressure and room temperature. Then, the state of the polishing agentwas visually observed.

∘: No supernatant or precipitate generated

X: Supernatant and precipitate generated

(Production Example of Organic Particles 1)

To separable flask equipped with a stirrer, a thermometer and a refluxcondenser were fed 2,000 parts of water and 0.4 part of ammonium alkyldiphenyl ether disulfonate. The resulting mixture was stirred and heatedto 70 degree centigrade while replacing with nitrogen. The internaltemperature was kept at 70 degree centigrade and 5.2 parts of 10%azobiscyanovaleric acid aqueous solution neutralized with ammonia wasadded as a polymerization initiator. Separately, 216 parts of ethylacrylate, 72 parts of methacrylic acid and 1.8 parts of n-dodecylmercaptan were mixed and the mixture was added dropwise to the flaskover 4 hours. After 30 minutes, 72 parts of styrene was added to theflask over 15 minutes and the resultant was kept at 70 degree centigradefor 4 hours.

The resulting emulsion had 13.5% of a solid content, an average particlediameter of 170.4 nm which was measured by light scattering, and pH of5.0. The SEM image of the resulting organic particles is shown in Table1.

(Production Example of Organic Particles 2)

To separable flask equipped with a stirrer, a thermometer and a refluxcondenser were fed 547.3 parts of water and 0.3 part of ammonium alkyldiphenyl ether disulfonate. The resulting mixture was stirred and heatedto 70 degree centigrade while replacing with nitrogen. The internaltemperature was kept at 70 degree centigrade and 1.2 parts of ammoniumpersulfate was added as a polymerization initiator. Separately, 222.2parts of methyl methacrylate, 59 parts of methacrylic acid and 15 partsof divinyl benzene were mixed to 120 parts of water and 0.25 part ofammonium alkyl diphenyl ether disulfonate to produce an emulsion of themonomers. This emulsion was added dropwise to the flask over 4 hours andthen kept at 70 degree centigrade for 30 minutes. Subsequently, 60 partsof styrene, 23.7 parts of water and 0.05 part of ammonium alkyl diphenylether disulfonate were mixed. The resulting adjusted emulsion was addeddropwise thereto over 15 minutes and kept at 70 degree centigrade for 4hours.

The resulting emulsion had 32.6% of a solid content, an average particlediameter of 140 nm which was measured by light scattering, and pH of2.9.

(Production Example of Organic Particles 3)

To separable flask equipped with a stirrer, a thermometer and a refluxcondenser were fed 434.5 parts of water and 0.1 part of ammonium alkyldiphenyl ether disulfonate. The resulting mixture was stirred and heatedto 70 degree centigrade while replacing with nitrogen. The internaltemperature was kept at 70 degree centigrade, and 0.4 part of ammoniumpersulfate was added as a polymerization initiator and its dissolutionwas confirmed. Separately, 30 parts of methyl acrylate, 27.2 parts ofbutyl acrylate, 37.3 parts of acetoacetoxyethyl methacrylate and 5.5parts of 2-hydroxyethyl methacrylate were mixed to 40 parts of water and0.1 part of ammonium alkyl diphenyl ether disulfonate to produce anemulsion of the monomers. This emulsion was added dropwise to the flaskover 4 hours. After 30 minutes, 10 parts of 2-ethylhexyl acrylate, 10parts of butyl methacrylate, 8 parts of water and 0.02 part of ammoniumalkyl diphenyl ether disulfonate were mixed. The resulting adjustedemulsion was added dropwise over 15 minutes and kept at 70 degreecentigrade for 4 hours.

The resulting emulsion had 19.8% of a solid content, an average particlediameter of 183 nm which was measured by light scattering, and pH of3.2.

Comparative Production Example 1 of Organic Particles

To separable flask equipped with a stirrer, a thermometer and a refluxcondenser were fed 547.3 parts of water and 0.3 part of ammonium alkyldiphenyl ether disulfonate. The resulting mixture was stirred and heatedto 70 degree centigrade while replacing with nitrogen. The internaltemperature was kept at 70 degree centigrade, and 1.2 parts of ammoniumpersulfate was added as a polymerization initiator. Separately, 169.5parts of styrene, 41 parts of methyl methacrylate, 85.6 parts of butylacrylate and 60.5 parts of methacrylic acid were mixed to 142 parts ofwater and 0.3 part of ammonium alkyl diphenyl ether disulfonate toproduce an emulsion of the monomers. This emulsion was added dropwise tothe flask over 4 hours and thereafter it was kept at 70 degreecentigrade for 4 hours.

The resulting emulsion had 34.2% of a solid content, an average particlediameter of 140.8 nm which was measured by light scattering, and pH of2.4. A SEM image of the obtained organic particles is shown in FIG. 2.

Example 1

The pH of a 10% oxalic acid solution was adjusted to 7.2 using ammonia.This solution, the emulsion after pH adjustment in Production Example 1,pure water, 30% hydrogen peroxide and benzotriazole were well mixed soas to adjust an organic particle (solid content) concentration to be 5.0weight %, hydrogen peroxide to be 2.0 weight %, oxalic acid to be 1.0weight %, pH to be 7.2 and benzotriazole to be less than 0.1 weight %.The polishing results are shown in Table 1.

Example 2

The pH of a 10% oxalic acid solution was adjusted to 7.2 using ammonia.This solution, the emulsion after pH adjustment in Production Example 2,pure water, 30% hydrogen peroxide and benzotriazole were well mixed soas to adjust an organic particle (solid content) concentration to be 5.0weight %, hydrogen peroxide to be 2.0 weight %, oxalic acid to be 1.0weight %, pH to be 7.2 and benzotriazole to be less than 0.1 weight %.The polishing results are shown in Table 1.

Example 3

The pH of a 10% oxalic acid solution was adjusted to 7.2 using ammonia.This solution, the emulsion after pH adjustment in Production Example 3,pure water, 30% hydrogen peroxide and benzotriazole were well mixed soas to adjust an organic particle (solid content) concentration to be 5.0weight %, hydrogen peroxide to be 2.0 weight %, oxalic acid to be 1.0weight %, pH to be 7.2 and benzotriazole to be less than 0.1 weight %.The polishing results are shown in FIG. 1.

Example 4

The pH of a 10% glycine solution was adjusted to 7.5 using ammonia. Thissolution, the emulsion after pH adjustment in Production Example 1, purewater, 30% hydrogen peroxide and benzotriazole were well mixed so as toadjust an organic particle (solid content) concentration to be 5.0weight %, hydrogen peroxide to be 2.0 weight %, glycine to be 1.0 weight%, pH to be 7.2 and benzotriazole to be less than 0.1 weight %. Thepolishing results are shown in Table 1.

Example 5

The pH of a 10% asparatic acid solution was adjusted to 7.6 usingammonia. This solution, the emulsion after pH adjustment in ProductionExample 1, pure water, 30% hydrogen peroxide and benzotriazole were wellmixed so as to adjust an organic particle (solid content) concentrationto be 5.0 weight %, hydrogen peroxide to be 2.0 weight %, asparatic acidto be 1.0 weight %, pH to be 7.2 and benzotriazole to be less than 0.1weight %. The polishing results are shown in Table 1.

Comparative Example 1

The pH of a 10% oxalic acid solution was adjusted to 7.2 using ammonia.This solution, the emulsion after pH adjustment in ComparativeProduction Example 1, pure water, 30% hydrogen peroxide andbenzotriazole were well mixed so as to adjust an organic particle (solidcontent) concentration to be 5.0 weight %, hydrogen peroxide to be 2.0weight %, oxalic acid to be 1.0 weight %, pH to be 7.2 and benzotriazoleto be less than 0.1 weight %. The polishing results are shown in Table1.

Comparative Example 2

The operation and evaluation were carried out in the same manner as inExample 1, except that commercial colloidal silica (PL-1, a product ofFuso Chemical Co., Ltd.) was substituted for the organic particle inExample 1. The polishing results are shown in Table 1.

TABLE 1 Polishing Rate Dishing Erosion Storage (Å/min) Scratch (Å) (Å)Stability Example 1 3800 ◯ 400 220 ◯ Example 2 3700 ◯ 400 240 ◯ Example3 3500 ◯ 380 210 ◯ Example 4 3200 ◯ 370 200 ◯ Example 5 3100 ◯ 350 190 ◯Comparative 4200 ◯ 2600 1200 ◯ Example 1 Comparative 3900 X 3700 2200 XExample 2

INDUSTRIAL APPLICABILITY

The polishing slurry of the present invention is capable of polishing anexcess metal film on a wiring pattern-formed insulation film with a highrate, capable of polishing without causing any damage or scratch due topolishing excess on a surface of a substance to be polished, and capableof polishing which produces high smoothness of the surface without anyunevenness due to dishing, erosion or the like.

Furthermore, since the polishing slurry of the present invention with asolid content composition containing organic fine particles has aconsiderably lower decomposition temperature than that of the insulationfilm, it can be subjected to thermal treatment and plasma treatment andit is possible to remove the residue of a polishing agent withoutdamaging the insulation film. Therefore, its industrial applicability isvery high.

1. A polishing slurry comprising organic particles (A), wherein saidorganic particles (A) are those obtained by coating a part of thesurface of an organic particle (B) having functional groups capable ofreacting with a metal to be polished on the surface with a resin (C)free from functional groups capable of reacting with a metal to bepolished.
 2. The polishing slurry according to claim 1, furthercomprising an oxidizing agent.
 3. The polishing slurry according toclaim 1, wherein said organic particle (B) contains a copolymer obtainedby polymerization of a monomer composition comprising 1 to 50 weight %of one, two or more monomers selected from a monomer having a carboxylicacid group, a monomer having a hydroxyl group, a monomer having an aminogroup, a monomer having an acetoacetoxy group and a monomer having aglycidyl group, and 99 to 50 weight % of other monomers, with eachpercentage based on the total weight of the monomers.
 4. The polishingslurry according to claim 1, wherein the resin (C) contains a polymer ofa styrene type monomer and/or a (meth) acrylic acid ester type monomer.5. The polishing slurry according to claim 2, wherein the polishingslurry further comprises at least one complexing agent selected fromcarboxylic acids, amines, amino acids and ammonia, and its pH is in therange of 5 to
 11. 6. The polishing slurry according to claim 1, whereinthe oxidizing agent is hydrogen peroxide.